This invention relates to the field of hearing protection capable of excluding noise and other sounds from the ears of a protected person.
Persons obligated to work in loud noise environments are known to incur premature hearing loss and other abnormal medical conditions. In the past, workers who participated in the riveting of heavy structures, steam locomotive engineers, saw mill operators and certain types of mineral miners provided notable examples of hearing loss originating in prolonged exposure to impact and other high intensity noises. In modern times, persons working on aircraft flight lines, in electrical power generation plants, crewmembers in Navy gun turrets and armored tank crewmembers are typical of those found to be susceptible to noise-induced hearing loss. The recent advent of Occupational Safety and Health Administrations (OSHA) in the federal and state governments has increased the awareness and knowledge needed in preventing prolonged exposure hearing injuries. The OSHA rules relating permissible exposure time inversely with noise intensity have been particularly effective in diminishing the incidence of work-related hearing injuries.
Such new awareness together with the inherent preference of human workers to be minimally encumbered with bulky and heavy hearing protection apparatus has created an ongoing need for improved hearing protection arrangements, preferably arrangements based on new technology protective concepts. The need for such new concepts in hearing protection is particularly acute in many military situations where such complexities as confined space, long mission durations, frequent personnel changes, and a need to communicate with heating protected persons add complexity to the hearing protection problem.
The absence of a fully satisfactory hearing protection arrangement in the prior art is exemplified by the number of different hearing protection devices found in prior patents. Among these previous hearing protection arrangements is the ear protector of E. Simon et al, shown in U.S. Pat. No. 2,782,423. The Simon apparatus is similar to the earphone devices used in radio and telegraph communications. The Simon apparatus includes ear enclosing pads which are fabricated from a plastic foam, preferably an isocyanate plastic foam capable of absorbing sound energy and particularly the sound emitted by an aircraft jet engine.
The patent of R. E. Ulrich et al, U.S. Pat. No. 2,990,553, discloses an ear protection arrangement employing a paste-like consistency liquid mixture as a sound attenuating medium.
In the patent of F. P. Beguin, U.S. Pat. No. 3,644,939, is disclosed a hearing protector ear cup provided with a venting arrangement that is compatible with achieving low frequency sound attenuation. The Beguin patent includes a cup-like cavity and a resilient padding member for engagement with the ear adjacent skin tissue of a user subject.
The patent of E. L. Davidson et al, U.S. Pat. No. 3,845,505, describes a suspension arrangement for adjusting the position of noise attenuating ear cups with respect to an attached safety helmet. The Davidson et al sound attenuation material is made from foam rubber or plastic and is incorporated within a cup-like receptacle.
In the patent of W. G. Morton, U.S. Pat. No. 4,114,197, a safety helmet having an ear protecting sub-portion is disclosed. The Morton protector includes inner and outer cavity members in a double walled structure intermediate the user's ear and an external source of sound. The inner cavity in the Morton apparatus is fitted with a resilient member which contacts the skin of the user's cranial surface.
Although each of these previously patented hearing protection arrangements employs a cup-like structure and a suspension arrangement similar to that used in the present invention, none of these prior devices achieves the advantages of sound attenuation through the present invention's non-conductive medium.